Telecommunications heretofore has used massive buried conduits which enclose many pairs of conductors. A single pair provides telephone service to a single resident or office telephone system. Such cables are typically armored cables which are buried several feet below ground, and when they become sufficiently large, they are buried inside large tile pipes having a number of parallel passages therethrough. Periodically, it is necessary to interconnect conduits at underground facilities. With the advent of fiber optics, size of the conduit can be reduced substantially. Rather than a large armored cable of substantial weight holding hundreds or perhaps thousands of pairs of conductors, a more convenient approach is now available, namely a small optical fiber which is able to carry a large number of communications paths. While there is only a single optical fiber in a minimum installation, it can transmit multitudinous isolated signals and provide the equialent of several hundred pairs of conductors. Typically, an optical fiber to be buried underground is first placed inside a fairly large diameter plastic tubing or pipe. It serves as a guide and provides protection against the intrusion of water, collapsing under the overhead burden and the like. Periodically, the optical signal must be boosted and to this end, it is necessary to periodically interrupt the fiber with laser generators. This equipment typically includes the necessary switch gear to route several conductor pair equivalents on alternate system routes. Thus, the optical fiber at such an equipment installation may pick up several other lateral optical fibers, or perhaps the old styled armored cable having individual conductor pairs. In any event, it is necessary to install a set of switch gear which provides appropriate interconnection from individual pairs into the optical fiber transmission system. Such equipment also must typically enclose and house a laser generating system which forms the light placed on the optical fiber for transmission of the modulated signal.
With this background in mind, it should then be observed that the optical fiber transmission system periodically must connect with a buried vault to thereby house the laser generating apparatus and also the switch gear necessary for connecting individual conductor pairs into the system. The vault must be fairly rugged and durable to exclude the external atmosphere to thereby house and protect the more sensitive electronic equipment. This includes the laser generating devices and the switch gear necessary for connection of a multitude of conductor pairs. This requires an environmentally regulated interior. Heretofore, such a structure has been fabricated something in the fashion of a storm shelter. Typically, it is assembled above the surface and is made of separable sections. The ordinary construction heretofore has been a skeleton made of reinforcing bars or wire mesh with concrete walls. This provided a very strong structure which is able to hold up the weight of the burden and to provide the necessary safe environmental climate. A typical construction has provided internal dimensions upwards of 24' length by perhaps 6' width and a ceiling height of 9'. Because the wall thickness is relatively thick to assure a substantial structure, the gross weight is approximately 40 tons or more. Handling a 40 ton structure is somewhat difficult; often such concrete vaults have been fabricated in sections for easier transport. Then, at the time of installation and burial, it is necessary to assemble the sections together with some kind of sealant between the sections to assure exclusion of artesian water.
This structure is directed to a vault providing substantial structural strength with a built up wall thereby assuring exclusion of ground water. Moreover, it enables an isolated interior so that the environment can be totally controlled. This enables the fabrication of what is in actual practice a seamless structure which therefore requires no joint seals at the time of installation. In a device of comparable size, the weight is reduced by almost 70,000 pounds, or at least 35 tons weight reduction. This simplifies transportation, and reduces the size of the handling equipment for installation.
One reference of a protective system is set forth in U.S. Pat. No. 3,650,795. Certain mechanical and chemical properties are obtained through the use of this system. It does not necessarily lend itself to the type of buried vault which is set forth in the present disclosure. Another reference of note is U.S. Pat. No. 3,695,968. This discloses a built-up plywood layer with an encapsulation system. U.S. Pat. No. 4,123,582 is directed to a multi-layer system using a polymeric film in the method of construction to yield a multi-layered device. In U.S. Pat. No. 4,443,520 a coating for combustible materials (wood and the like) yields fireproofing by the use of alumina and glass fibers to form a refractory coating. The composite materials set forth in this disclosure provide a strong and durable structure which is able to sustain the weight of the burden overhead and yet isolates the atmosphere to define a controlled environment. The structure further yields a seamless type construction which does not require joint sealing and the like. This permits the delicate electronic equipment to be installed on the interior and connected with an optical fiber for transmission of telecommunication signals. All the optical fiber distribution system and the associated electronic equipment is thus buried underground and therefore is made safe and secure from inclement weather, protected from vandalism and is otherwise assured of the best operating conditions.
The present invention is summarized as a buried vault having an interior sufficiently large and configured for installation of laser generating equipment and the associated electronics for telecommunication systems communicating through optical fibers, and is otherwise constructed with a closed chamber. There is a chimney portion which is adapted to extend upwardly to provide easy access through a closed entry. Further, the chimney encloses an outlet for venting of heating and air conditioning equipment. The device is constructed in a seamless fashion with multiple layers of woven roving and fiberglass matting to define multiple sheets which are joined together with a suitable polymeric resin. This defines an interior surface of the structure. A light weight core in sheet form is placed over this, and the exterior is then applied with a curable polymeric resin having randomly distributed random length cuts of chopped fiberglas and layers of woven roving and fiberglas matting. On the interior, a gel coating is provided to assure easy mold release. The structure is fabricated to define a vault of the described construction having such a chimney. Ideally, the device is fabricated in such a fashion as to be seamless in construction. At this juncture, the only points of entry are those formed to receive the optical fiber cables and conduits, and the chimney is constructed with a vent and hatch for human entry.